Answer:
12
Step-by-step explanation:
If you flip the polygon on the right so it looks like the polygon on the left, the scale factor for the small polygon to the big polygon is 32/40 or 4/5.
Now use that scale factor, 4/5, to find the missing length
4/5 = ?/15
5*3 = 15 so 4*3 = ?
? = 12
